This invention relates to a utility conveyance, such as a pipe or cable, especially designed for burial.
Many utilities, such as ATandT, bury their pipes and cables (xe2x80x9cutility conveyancesxe2x80x9d) underground both for reasons of safety and esthetics. Underground burial provides protection to such utility conveyances against weather and other sources of potential damage. Utilities that undertake burial of their conveyances usually make extensive efforts to plot the location of each buried conveyance on a map to facilitate its location in case of repair or replacement. While a map will indicate the general location of a buried conveyance, more precise location information often becomes necessary, particularly in urban environments. For that reason, most utilities that bury their conveyances underground typically rely on electromagnetic signaling techniques to precisely locate such conveyances.
U.S. Pat. No. 5,644,237, issued in the names of Hossein Eslambolchi and John Huffman, on Jul. 1, 1997, and assigned to ATandT, (incorporated by reference herein) discloses an electromagnetic signaling technique for locating a buried utility conveyance. A signal generator applies a locating signal and a confirmation signal to a metallic part of the conveyance. In the case of an optical fiber cable, the metallic part comprises either a metallic sheath or a copper trace wire within the cable. Using a signal detector, a technician detects both the locating signal and the confirmation signal radiated above ground to precisely locate the buried conveyance.
After locating a buried conveyance, a technician for the utility will typically mark the surrounding area with an environmentally benign paint to alert an excavating contractor of the presence of the buried conveyance. By industry agreement, utilities have standardized on certain colors to mark the following:
Most jurisdictions require contractors seeking to excavate in a particular area first undertake to contact the affected utilities prior to digging so that each may mark its buried conveyance(s). Thus, the contractor will know what type of utility conveyance or activity is present and can take the appropriate precautions prior to digging based on the color employed to mark the affected area. Unfortunately, some contractors fail to contact the affected utility. A utility, even if contacted by a contractor, may fail to mark the affected area. Either failure will have disastrous consequences if a contractor, unaware of the conveyance, begins to excavate and causes damage.
This, there is need for an additional warning mechanism for alerting a contractor of the existence of a buried utility conveyance which does not require the intervention of either the contractor or the utility.
Briefly, in accordance with a preferred embodiment, there is provided a passive warning mechanism associated with a utility conveyance, typically in the form of a pipe, duct or cable, for burial in surrounding earth. The warning mechanism takes the form of a water-soluble material, typically a water-soluble environmentally benign dye, carried by the conveyance. The water-soluble material, upon exposure to moisture, will bleed from the conveyance into the surrounding earth to mark the surrounding earth a distinctive color. Thus, a contractor starting to excavate in the vicinity of the conveyance will notice the dye-colored surrounding earth and thus become aware of the presence of the buried conveyance, thus taking appropriate action to avoid possible damage.